Statistical evaluation of rapeseed methyl ester as ignition improver in an 11 liters ethanol fuelled diesel engine

There is an ongoing search for better and cheaper ignition improvers to facilitate the introduction of ethanol fuel. Rapeseed methyl ester (RME) was therefore investigated in an ethanol fueled compression-ignited engine by means of different statistical designs. Experiments were accordingly performed at various levels of speed, load and concentration of RME in ethanol while the emissions were measured. The optimization criterions were; satisfactory engine performance and low exhaust emissions. Initial experiments showed that the power outlet and the opacity increased when using the tested ignition improver. A three level full factorial design correctly predicted that the emissions of HC, CO and NOX, should increase when using RME as an ignition improver. Lowest level of exhaust emissions was obtained at 16 % RME in ethanol but a higher concentration should be used to obtain better engine performance. A general conclusion is that RME seems suitable for the investigated task, i.e. ignition improvement, but the opacity increment should be further studied. Careful selection of the conditions used as well as rigorous control of the engine and dynamometer is necessary to obtain good repeatability and accuracy of the experimental conditions.<p>Godkänd; 2008; 20090126 (ysko)